Generally, an internet based communication system includes a protocol stack consisting of five layers. And, a configuration of each protocol layer is shown in FIG. 1.
FIG. 1 is a diagram for one example of an internet protocol stack used in general.
Referring to FIG. 1, an internet protocol stack consists of an application layer (i.e., a most upper layer), a transport layer, a network layer, a link layer and a physical layer in order. The application layer is the layer for supporting such a network application as FTP (File Transfer Protocol), HTTP (Hypertext Transfer Protocol, TCP (Transmission Control Protocol), UDP (User Datagram Protocol) and the like. The transport layer is the layer responsible for an inter-host data transport function using TCP/UDP. The network layer is the layer for setting a data transport path from a source to a destination via the transport layer and IP protocol. The link layer is the layer responsible for data transmission between neighbor network entities and MAC (medium access control) via PPP/Ethernet protocol and the like. And, the physical layer is a lowest layer for performing a data transmission by a bit unit using a wire/wireless medium.
FIG. 2 is a diagram for operation of each layer for data transmission used in general.
Referring to FIG. 2, a transport layer of a transmitting side generates a new data unit by adding header information H+ to a message payload M received from an application layer that is an upper layer. The transport layer transfers the new data unit to a network layer that is a lower layer. The network layer generates a new data unit by adding header information Hn used by the network layer to the data received from the transport layer and then transfers this data unit to a link layer that is a lower layer.
Subsequently, the link layer generates a new data unit by adding header information H1 used by the link layer to the data received from the upper layer and then transfers it to a physical layer that is a lower layer. The physical layer transfers the data unit received from the link layer to a receiving side.
Meanwhile, a physical layer of the receiving side receives the data unit from the transmitting side and then transfers the received data unit to a link layer that is an upper layer of the physical layer. The receiving side processes a header added to each layer and then transfers the header removed message payload to an upper layer. Through this process, data transceiving is performed between the transmitting side and the receiving side.
For the data transceiving between the transmitting side and the receiving side, as shown in FIG. 2, each layer adds a protocol header and then performs such a control function as data addressing, routing, forwarding, data retransmission and the like.
FIG. 3 is a diagram of a protocol layer model defined in a wireless mobile communication system based on IEEE 802.16 system used in general.
Referring to FIG. 3, a MAC layer belonging to a link layer can consist of three sublayers.
First of all, a service-specific convergence sublayer (service-specific CS) modifies external network data received via a convergence sublayer service access point (CS SAP) into MAC SDUs (service data units) of a MAC sublayer (common part sublayer: CPS) or maps the corresponding data. This layer can include a function of sorting SDUs of external network and then linking a corresponding MAC service flow identifier (SFID) with a connection identifier (CID).
Secondly, a MAC CPS is a layer of providing such a core function of the MAC as system access, bandwidth allocation, connection setting and management and the like. The MAC CPS receives data sorted by a specific MAC connection from various convergence sublayers via the MAC SAP. In this case, a QoS (quality of service) is applicable to the data transmission and scheduling via a physical layer.
Thirdly, a security sublayer is able to provide such a function as authentication, security key exchange and encryption.
The MAC layer is a connection-oriented service and is implemented with the concept of transport connection. When a mobile station registers with a system, a service flow can be provided by a negotiation between a mobile station and a system. If a service request is changed, a new connection can be set. In this case, the transport connection defines mapping between peer convergence processes using MAC and service flow. And, the service flow defines QoS parameters of MAC PDU exchanged in the corresponding connection.
The service flow on the transport connection plays a core role in managing and operating the MAC protocol and provides a mechanism for uplink and downlink QoS managements. In particular, service flows can be combined with a bandwidth allocation process.
In the general IEEE 802.16 system, a mobile station is able to have a 48-bit universal MAC address for each radio interface. This address uniquely defines a radio interface of a mobile station and is usable to set an access of the mobile station during an initial ranging process. Since a base station verifies mobile stations using different identifiers (ID) of the mobile stations, respectively, the universal MAC address is usable as a portion of an authentication process.
Each connection can be identified by a 16-bit connection identifier (CID). While initialization of a mobile station is in progress, two management connection pairs (i.e., uplink and downlink) are established between a mobile station and a base station. And, three pairs including the management connections are selectively usable.
In order for a transmitting stage and a receiving stage to exchange data with each other in the above described layer structure, assume a case of transmitting MAC SDUs (medium access control service data units). In this case, the MAC SDU is processed into MAC PDU (medium access control packet data unit). In order to generate such a MAC PDU, a base station or a mobile station enables a MAC header to be included in the corresponding MAC PDU.